US Patent 4,758,423: Scope, Claims, Expiration, and Ergot Alkaloid Nasal Spray Patent Landscape

US Patent 4,758,423 covers a nasal spray applicator preloaded with an ergot peptide alkaloid, including dihydroergotamine, bromocriptine, dihydroergocristine, and dihydroergotoxine. The claims reach the combination of the applicator, the nasal formulation, the active ingredient, and specified dose or formulation characteristics. The patent issued on July 19, 1988, and its ordinary pre-URAA term would have expired in 2005. It therefore has no current blocking effect, although it remains relevant as prior art and as a historical foundation for nasal dihydroergotamine products.

What does US Patent 4,758,423 cover?

The patent protects a drug-device combination rather than a bare ergot alkaloid molecule.

The core claimed combination has four elements:

A nasal applicator.
An ergot peptide alkaloid composition contained in the applicator.
A therapeutically effective amount of the active ingredient per unit dose.
An applicator adapted to deliver the unit dose to the nasal mucosa.

Claim 1 is the broadest independent claim. It covers either:

Dihydroergocristine; or
An ergot peptide alkaloid within the specified Markush formula; or
A pharmaceutically acceptable acid-addition salt of those compounds.

The claim also requires a pharmaceutically acceptable carrier suitable for nasal administration.

The patent does not broadly claim every nasal formulation containing every ergot-derived compound. Its scope is limited by the chemical definitions in the Markush formula and by the requirement that the composition be associated with a nasal spray applicator.

What compounds are expressly covered by the patent?

The dependent claims identify several compounds by name.

Claim	Compound or limitation	Practical scope
1	Dihydroergocristine and defined ergot peptide alkaloids	Broad composition and applicator combination
2	0.1 to 5 mg per unit dose	Dose limitation
3	Dihydroergotamine	Directly covers nasal DHE products
4	Bromocriptine	Directly covers nasal bromocriptine products
5	Dihydroergotoxine	Directly covers nasal dihydroergotoxine products
6	0.1 to 5 mg per administration	Administration-dose limitation
7	Liquid formulation	Liquid nasal spray
8	0.1 to 5 mg/mL	Concentration limitation
9	Propellant	Propellant-containing formulation
10	Halogenated hydrocarbon propellant	Specific propellant limitation
11	Aqueous solution with viscosity-increasing agent	Mucoadhesive or viscosity-enhanced formulation
12	Methyl cellulose	Specific viscosity agent
13	Non-aqueous solvent	Non-aqueous liquid formulation

The named dihydroergotamine claim is commercially the most significant. Dihydroergotamine mesylate is used for acute migraine treatment, and nasal delivery was developed to avoid gastrointestinal absorption and provide a noninjectable route.

How should claim 1 be interpreted?

Claim 1 is a combination claim with a relatively broad formulation perimeter but a narrower infringement trigger.

“Consisting essentially of”

The phrase “consisting essentially of” generally permits additional ingredients that do not materially alter the basic and novel characteristics of the claimed invention. The phrase is narrower than “comprising” but broader than “consisting of.”

A formulation containing buffers, preservatives, stabilizers, solvents, tonicity agents, or other conventional excipients could fall within the claim if those ingredients do not materially change the claimed nasal applicator and ergot-alkaloid delivery system.

A formulation with a materially different delivery mechanism, a non-nasal route, or a different active pharmaceutical ingredient would have a stronger noninfringement position.

“Nasal applicator”

The claim is directed to an applicator containing the formulation. It does not require a particular pump, valve, nozzle, metering chamber, container material, or actuation mechanism.

The absence of detailed mechanical limitations makes the apparatus portion of the claim comparatively broad. A pump spray, metered-dose device, or other nasal delivery container could potentially satisfy the applicator limitation if it is adapted to administer the claimed unit dose to nasal mucosa.

“Per unit dose”

The claim requires a therapeutically effective amount per unit dose. Claims 2 and 6 specify the range of 0.1 to 5 mg. Claim 8 separately specifies 0.1 to 5 mg per milliliter for a liquid formulation.

The dose limitations create potential design-around space. A product delivering less than 0.1 mg or more than 5 mg may avoid claims 2 and 6, but it could still be evaluated against claim 1 if the dose remains therapeutically effective.

“Suitable for nasal spray administration”

The carrier must be pharmaceutically acceptable and suitable for nasal spray administration. A formulation intended for injection, oral use, transdermal delivery, or pulmonary inhalation would not satisfy this limitation merely because it contains the same active ingredient.

What formulations are protected by US 4,758,423?

The dependent claims cover three principal formulation classes.

Liquid aqueous formulations

Claims 7, 8, 11, and 12 cover liquid formulations, including aqueous solutions containing a viscosity-increasing agent. Methyl cellulose is expressly identified in claim 12.

The viscosity limitation may be relevant to formulations designed to increase nasal residence time, reduce runoff, or improve dose retention on the nasal mucosa.

Propellant formulations

Claims 9 and 10 cover compositions containing a propellant acceptable for nasal administration, including a halogenated hydrocarbon.

This portion of the patent reflects older metered spray technology. Modern nasal products may use mechanical pumps or alternative propellant systems, which could avoid the specific limitations of claims 9 and 10 while remaining within claim 1 if all other elements are satisfied.

Non-aqueous formulations

Claim 13 covers a formulation using a non-aqueous solvent. The claim does not specify the solvent by name. The solvent would still need to be pharmaceutically acceptable and suitable for nasal spray administration.

Does the patent cover a method of treating migraine?

The claims supplied do not recite a treatment method. They claim a nasal spray applicator and associated composition.

That distinction matters:

A method of administering dihydroergotamine to treat migraine is not expressly claimed.
A composition sold in a nasal applicator can implicate the apparatus claims.
A bulk vial, concentrate, or active ingredient sold without the claimed applicator may present a different infringement analysis.
A method-of-use patent would require separate claim language directed to treating a disease or administering the drug for a specified indication.

The patent’s commercial value therefore depended on the combination of formulation and delivery device, not on exclusive ownership of dihydroergotamine or migraine treatment generally.

When did US Patent 4,758,423 lose exclusivity?

The patent issued on July 19, 1988. Because it was a pre-June 8, 1995 patent, its ordinary term was generally 17 years from issue under the pre-URAA patent-term regime. On that basis, the patent expired on July 19, 2005, subject to any applicable patent-term adjustment, terminal disclaimer, or patent-term extension.

Event	Date or period
Patent issuance	July 19, 1988
Ordinary pre-URAA term	17 years from issue
Ordinary expiration	July 19, 2005
Current enforceability	Expired
Current Paragraph IV relevance	None for this patent
Current Orange Book blocking effect	None from this expired patent

An expired patent cannot support an injunction or damages claim for post-expiration infringement. It can remain relevant as prior art against later patent applications covering nasal ergot formulations, delivery devices, dosing regimens, or manufacturing processes.

What is the Orange Book status of the patent?

An Orange Book listing does not extend patent life. If US 4,758,423 was listed for an approved nasal dihydroergotamine product, the listing would have ceased to create a current exclusivity barrier when the patent expired.

For small-molecule products, Orange Book patent disputes generally arise through an abbreviated new drug application, or ANDA, and Paragraph IV certification. A generic applicant may certify that a listed patent is invalid, unenforceable, or will not be infringed. The patent owner may then bring an action under 21 U.S.C. § 271(e)(2), triggering a potential 30-month stay under the Hatch-Waxman framework.

That mechanism is no longer commercially operative for US 4,758,423 because the patent has expired. A current generic applicant cannot be blocked by this patent through a new Paragraph IV suit.

Were there Paragraph IV challenges to US 4,758,423?

The supplied claims and patent record do not establish a current Paragraph IV dispute involving US 4,758,423. Any historical ANDA litigation would need to be evaluated against the relevant product’s FDA listing, the patent-listing history, and federal court docket records.

The legal significance is clear even without a current challenge:

A Paragraph IV certification against an expired patent does not create a meaningful present-day market barrier.
A patent expiration certification under section vi is generally the relevant route for an expired listed patent.
Later patents covering a nasal device, formulation, manufacturing method, or dosing regimen can create separate Paragraph IV exposure.

What is the patent strength of US 4,758,423?

The patent had meaningful historical breadth but limited present commercial strength.

Historical strengths

The patent combined:

A broad genus of ergot peptide alkaloids.
Express coverage of dihydroergotamine.
Broad nasal applicator language.
Dose, concentration, solvent, propellant, and viscosity-dependent claims.
Coverage of both aqueous and non-aqueous formulations.

The absence of detailed pump or nozzle limitations reduced the number of mechanical design constraints.

Historical weaknesses

The patent also had vulnerabilities:

The chemical Markush definition may have raised written-description or enablement questions for compounds not specifically exemplified.
The “therapeutically effective amount” limitation can introduce factual disputes.
“Suitable for nasal spray administration” is functional language dependent on formulation and device characteristics.
The dependent claims overlap in dose concepts, particularly claims 2 and 6.
Modern delivery systems may avoid claims 9 and 10 by eliminating the recited propellant.
The claims do not broadly protect a treatment method, a specific migraine regimen, or a particular commercial pump architecture.

Today, the patent’s enforceability strength is zero because the term has expired. Its prior-art significance remains substantial for later patents that attempt to claim the same nasal DHE concept at a high level.

How does the patent compare with later nasal dihydroergotamine products?

US 4,758,423 is an early platform patent. Later products may rely on separate intellectual property directed to:

Specific nasal pump architecture.
Bidirectional or breath-powered delivery.
Dose-metering controls.
Spray plume geometry.
Formulation pH and osmolality.
Stabilization of dihydroergotamine mesylate.
Preservative systems.
Device priming and dose counting.
Manufacturing and filling processes.
Label-specific migraine dosing regimens.

A product such as Migranal historically implicated the nasal DHE concept covered by the patent. Trudhesa, a later dihydroergotamine nasal product, uses a proprietary delivery system and may rely on later device and formulation patents. Those later rights must be analyzed separately from US 4,758,423.

Issue	US 4,758,423	Later nasal DHE estate
Active ingredient	Broad ergot class, expressly including DHE	Usually DHE mesylate or a defined DHE formulation
Delivery	Nasal applicator	Often specific pump or delivery platform
Formulation	Broad carrier language with selected dependent limitations	More detailed excipient and performance limitations
Dose	0.1 to 5 mg in dependent claims	Product-specific dose and administration regimen
Legal status	Expired	May include unexpired patents
Generic risk	No current risk from this patent	Depends on Orange Book listings and asserted patents
Biosimilar pathway	Not applicable	Not applicable to small-molecule DHE

Are biosimilars relevant to this patent?

No. Dihydroergotamine and the other claimed ergot alkaloids are chemically synthesized small molecules, not biologics.

The relevant regulatory pathway is an ANDA under section 505(j) of the Federal Food, Drug, and Cosmetic Act. The 351(k) biosimilar pathway does not apply.

The competitive risks are therefore:

Generic nasal sprays.
Authorized generics.
Reformulated nasal DHE products.
New nasal delivery devices.
Alternative migraine therapies, including CGRP antagonists, ditans, triptans, and injectable DHE.

What manufacturing and intellectual-property barriers remain?

The expired patent does not remove technical barriers. A competitor may still need to solve:

Accurate metering of a low-dose liquid spray.
Chemical stability of DHE or its salt.
Consistent spray content uniformity.
Device priming and dose retention.
Nasal tolerability.
Preservative compatibility.
Container-closure integrity.
Extractables and leachables.
Batch-to-batch spray performance.
FDA comparative-device requirements.

Those technical barriers can support later patents even though the original platform patent has expired. A later patent cannot revive US 4,758,423, but it can protect a specific implementation that was not claimed in the earlier patent.

What generic launch risks exist?

US 4,758,423 does not create a current generic launch risk because it is expired. The principal risks are instead regulatory and technical.

A generic nasal DHE applicant would need to assess:

Whether the reference listed drug remains eligible for an ANDA pathway.
Whether the applicant must demonstrate pharmaceutical equivalence in the device.
Whether the nasal spray device is sufficiently equivalent to the reference product.
Whether later patents are listed in the Orange Book.
Whether non-listed formulation or device patents could support separate litigation.
Whether manufacturing patents or trade secrets affect commercial launch.
Whether the product requires clinical or pharmacokinetic bridging beyond a conventional ANDA package.

The strongest current barrier would ordinarily come from later, unexpired device or formulation patents, not from US 4,758,423.

What licensing deals or settlements affect this patent?

The patent claims supplied do not identify a license, settlement, covenant not to sue, or commercial agreement. No such agreement can be inferred from the claims.

A complete transaction review would distinguish:

License agreements covering the original nasal ergot technology.
Product-specific agreements for Migranal or later DHE products.
Device licenses for proprietary nasal pumps.
ANDA settlements involving later Orange Book patents.
Patent assignments and security interests.
Manufacturing or supply agreements.

An agreement involving a later DHE product would not automatically transfer rights under US 4,758,423, particularly because the patent has expired.

Key Takeaways

US 4,758,423 claims a nasal spray applicator containing an ergot peptide alkaloid composition.
Dihydroergotamine is expressly covered by claim 3.
The patent also names bromocriptine and dihydroergotoxine.
Claim 1 is a combination claim requiring the active formulation and nasal applicator.
Dependent claims cover doses of 0.1 to 5 mg, liquid formulations, propellants, aqueous viscosity-enhanced formulations, methyl cellulose, and non-aqueous solvents.
The patent does not expressly claim a migraine-treatment method.
The patent issued July 19, 1988, and its ordinary term expired July 19, 2005.
It cannot currently block a generic launch or support a new Paragraph IV enforcement action.
Biosimilar analysis is irrelevant because the products are small molecules.
Current commercial exposure depends on later formulation, device, manufacturing, and method-of-use patents.
The patent remains important prior art for later nasal dihydroergotamine patent applications.

FAQs

Does US Patent 4,758,423 cover dihydroergotamine mesylate?

Yes, claim 3 expressly covers dihydroergotamine, and claim 1 covers pharmaceutically acceptable acid-addition salts. Dihydroergotamine mesylate would generally fall within the salt language if the other nasal applicator and formulation limitations are satisfied.

Can a company sell a nasal DHE product after expiration of US 4,758,423?

Yes. The patent’s expiration removes its exclusionary effect. The company must still address later patents, FDA requirements, device equivalence, manufacturing controls, and any applicable Orange Book listings.

Does the patent cover a nasal pump without medication?

No. The claims require an ergot peptide alkaloid composition contained in or associated with the nasal applicator. An empty device is outside the principal claimed combination.

Does claim 1 cover oral or injectable dihydroergotamine?

No. The claimed applicator must be adapted to administer the composition to the nasal mucous membrane. Oral and injectable products do not satisfy the nasal administration limitation.

Is US 4,758,423 a biosimilar patent?

No. It concerns small-molecule ergot alkaloids. Generic-drug and ANDA rules, rather than biosimilar rules, govern competing products.

References

United States Patent and Trademark Office. (1988). US Patent No. 4,758,423, Nasal spray applicator.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations.
U.S. Food and Drug Administration. (n.d.). Orange Book: Approved drug products with therapeutic equivalence evaluations.
U.S. Congress. (1984). Drug Price Competition and Patent Term Restoration Act of 1984, Pub. L. No. 98-417, 98 Stat. 1585.
U.S. Code, 35 U.S.C. §§ 154, 271(e)(2).
U.S. Food and Drug Administration. (n.d.). Dihydroergotamine mesylate nasal spray prescribing information.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	368881	⤷ Start Trial
Austria	A825477	⤷ Start Trial
Australia	3078377	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,758,423

Summary for Patent: 4,758,423